The failure of mammalian tissue to carry out its expected metabolic functions can occur as a result of known causes such as e.g., disease, congenital defect, natural causes, etc. The ability to surgically excise malfunctioning or biologically deceased tissue and subsequently replace the removed tissue with comparable replacement tissue from a tissue donor has been known in the medical field for many years. Similarly, various processes of transfusing healthy whole blood, collected from willing donors for placement into recipients whose blood supply has been naturally or artificially depleted, due either to a trauma related accident or disease, have been recognized in the medical field.
Biological tissues, including organs and whole blood, or its separate component fractions, hereinafter referred to collectively as biological matter, cannot survive outside of their natural environment without some form of storage or preservation.
Biological degradation of the removed biological matter begins almost immediately while awaiting implantation or introduction into a recipient, as the excised matter is subjected to new environments possessing varied concentrations of familiar and foreign gases and liquids. In an attempt to minimize such degradation due to the altering of the biological matter's delicate metabolic balance, many theories, to date, have been advanced. However, none of the existing technology resulting from these preservation theories has provided a satisfactory solution to the problem of "long-term" biological matter preservation. It should be understood that "long-term" storage or preservation in this field translates into preservation of the 1) living biological tissue and 2) whole blood, without significant biodegradation or other loss of its natural functional capability, for a period of time no less than ten days and sixty days respectively.
Early attempts to preserve excised tissue used some form of cryogenic treatment whereby the biological tissue or organ was frozen, then thawed. The problems of crystal formation, and molecular expansion causing cell rupture prompted investigators to first drain the excised tissue of its natural fluids and replace them with a plasma-like perfusate designed to behave as an "anti-freeze" within the organ or tissue. Significant problems remained, however, with respect to the perfusate. Many perfusates caused allergic reactions in the recipient and often led to the outright refusal of the organ tissue by the recipient's immune system.
The often encountered need to transport biological matter, in a preserved form, has led to further complications. Recipients, who are often in a weakened condition themselves, must hurriedly travel to the site of the excised organ, or, as is the usual case, the biological matter must be shipped to the site of the recipient.
There are currently available so-called "portable" biological transportation devices that maintain the metabolic function of the biological matter in transit, by either freezing the organ/tissue; i.e. bringing the temperature of the organ/tissue to 0.degree. C., or flowing a simulated plasma or perfusate through the organ, often at a low temperature, but above the freezing point. These transportation methods have met with reasonable success. However, the necessary time frame involved from organ/tissue excision to actual transplantation remains extremely short; usually an organ can be artificially preserved ex vivo for only 24-72 hours. As a result, recipients domiciled in outlying geographic areas often suffer the additional financial hardship of extensive travel, on short notice, to receive a transplant. In many instances, potential recipients are determined by the geographic location of the donor, making transplant operations a practical impossibility for many individuals in need of such treatment.
As stated in my earlier U.S. Pat. No. 4,473,552, there is also a need to preserve and transport mammalian whole blood in a process that does not require the damaging freezing step for such preservation. Simple refrigeration which only maintains blood in a usable condition for 21 days, is also unsatisfactory. Therefore, there is a need for a suitable container or support system to preserve blood at refrigeration temperatures in a suitable transportable container for a duration exceeding 60-days.
The known methods of living biological tissue preservation and transportation require either freezing the tissue after a pretreatment with a suitable perfusate to retard the otherwise damaging effects of the low temperatures required, or, continuously pumping a liquid or gaseous perfusate through the tissue to nourish it at temperatures above that of freezing. Various containers, some of which are conceivably transportable, have been devised to carry out these tissue preservation methods.
One early device, described by Peterson in U.S. Pat. No. 3,810,367, comprised a container designed to have a human organ placed in a sterile saline solution in one compartment, and kept at 0.degree. C. by a separate underlying ice-containing compartment. The organ compartment contained a removable liner comprised of materials inert to animal tissue. Toledo-Pereyra in U.S. Pat. No. 4,502,295 proposed another hypothermic organ storage unit that reduced the metabolic rate of the excised organs to be stored by maintaining the surrounding temperature within the storage receptacles from between 0.degree. to 7.degree. C. Ice was disclosed as the chilling means. The presence of a draining means, through which melted ice water could be removed, represented an improvement in the field. A further ice-cooled organ preservation device was described by Toledo-Pereyra in U.S. Pat. No. 4,242,883. This device also used ice to chill the container holding the organ awaiting transplantation (liver), as well as the perfusate being pumped through the organ. The device allegedly preserved the organ ex vivo for 24 hours. Bauer et al., in U.S. Pat. No. 4,745,759 describes a portable organ storage unit comprised of a thermoelectric (AC/DC) refrigeration system designed to maintain the temperature of the perfusate solution pumped through the stored organ at 4.degree. C.
Chilled gases have also been used as a refrigeration means in connection with organ storage devices. Toledo-Pereyra, in U.S. Pat. No. 4,471,629, proposed the use of chilled helium perfused into a kidney while the organ was subjected to a pressurized nitrogen environment. In this patent, the organ is frozen to a temperature between -70.degree. and -140.degree. C. A thawing format using microwaves is suggested. The disclosure of de Roissart, in U.S. Pat. No. 3,607,646 contemplates the use of an inert gas environment to surround an excised organ awaiting transplantation while simultaneously reducing the amount of excess oxygen from the perfusion fluid. Exposure of the organ to amounts of oxygen in the perfusion fluid of more than 10 percent is disclosed as having adverse effects on the organ's preservation. Kraushaar, in U.S. Pat. No. 4,008,754 teaches the use of an inert gas, both to fill the organ to be preserved, and as its surrounding atmosphere, prior to freezing the organ to temperatures below -100.degree. C. As is well known, any device which employs temperatures below 0.degree. C. is of little practical value for biological matter preservation because significant deterioration of the matter sought to be preserved is known to occur as a result of the freeze/thaw cycle.
The present invention provides a wider range of significant advantages over the prior art devices and methods for living biological matter preservation. It is applicable to the preservation of mammalian organs and other living biological tissue, as well as whole blood, or any component of such that contains or comprises living cells. The present device further uses a pneumatically powered micro-motor to recirculate a compressed air or pressurized inert refrigerant. This lowers the temperature of the chamber, or concave receptacle well containing the biological matter, to 1.degree.-3.degree. C. (or 34.degree.-37.degree. F.), thus eliminating the need for the elaborate thawing protocol made necessary when temperatures reach or drop below the freezing point. The use of a air, or recirculated inert gas refrigerant assures that the biological contents are cooled evenly, thus eliminating the danger of unequal temperature gradients within a preservation container. Such temperature differentiation can damage the living biological matter being preserved. When ice is used as the cooling agent, even the use of the best thermal conductive materials for the containers may allow a temperature gradient to exist within the container which endangers the viability of the preserved biological matter.
The presence and amount of available oxygen contained in the device is closely monitored by use of a sensor and readout means. A preferred preservative is hydroxyethyl starch (HES) or any preservative solution that will block and form a barrier surrounding healthy cells. The preservative completely surrounds the biological matter and fills the receptacle well thereby further inhibiting excess oxygen/ biological matter interaction.
The entire device is transportable. The micro-motor is powered by pneumatic bursts of circulated air or inert gas. The bursts are triggered by integrated instrumentation powered by a rechargeable battery pack. The device can also be used for stationary storage and have its micro-motor powered by pneumatic pressure supplied by the introduction of additional pressurized inert gases such as e.g., nitrogen, into the container via injection ports. The method of use and operation of the device is simple and inexpensive. The living biological matter stored in this invention can be preserved at ordinary refrigeration temperatures for extended periods of time, far greater in duration than contemplated in the prior art. Whole blood may be kept indefinitely according to the procedures disclosed herein, and other biological tissue including organs or living cells may be maintained in transplantable condition for a minimum of ten days. The metabolic processes of the stored living biological matter are, in effect, drastically lowered during preservation, and are restored in viable, usable form and returned to a body temperature of 98.6.degree. F.